Fluid reservoir with integrated heater

ABSTRACT

The present invention is directed to a fluid warming container (a.k.a., cassette) having an integrated heating element attached to the container, not the warming device as conventionally done. The heating element provides thermal energy to the fluid contained in the container. The fluid contained in the container is designed to be injected and/or delivered, eventually and normally immediately, into a patient.

FIELD OF THE INVENTION

The present invention relates to an apparatus for warming blood andother fluids to a desired temperature prior to introduction of the fluidinto a patient.

BACKGROUND OF THE INVENTION

Gaymar Industries, Inc., the assignee of this application, is theassignee of U.S. Pat. No. 5,875,282 (hereinafter referred to as “the'282patent”). The '282 patent is directed to an apparatus for warmingblood and other fluids to a desired temperature prior to introductioninto a patient. The blood and other fluids flow through a pathwaycontained by a bag. That pathway provides high flow performance andnormally provides uniform, gradual and energy efficient blood warming.The bag has a pair of guide rails and a warming device has a pair ofcorresponding apertures that work in conjunction to ensure the bag isproperly inserted into the warming device.

The warming device contains at least one, and normally a pair ofopposed, identical heater elements, a receptive slot down the middle ina horizontal plane with the possibility of two guide slots, one on eachside of the receptive slot. The optional guide rails align the bag so itcan be spaced and located precisely between the two heater elements. Thepair of guide rails, integrated into the sides of the bag, is parallelto one another providing sufficient rigidity for easy insertion of thebag, and being sized to allow easy insertion in only the correctorientation. The blood warmer preferably incorporates a microprocessorfor precise control of the electric current provided to the heater.Fluid temperature can be measured by contact of a RTD sensor with a thindielectric surface layer in contact with the bag and located proximal tothe fluid outlet and within the heater elements. By monitoring thetemperature of the fluid at the outlet of the bag, the temperaturecontroller can compute and provide a visual display of the fluidtemperature. In one embodiment, the sensed output temperature is aninput parameter to the controller of the heater elements. The deviceefficiently warms the fluid to about 37.5° C. for anticipated input to ahuman and, is simultaneously designed to prevent the fluid fromexceeding 42° C.

The apparatus disclosed in the '282 patent is a very good fluid warmingdevice but the applicants continue to try to improve it. One improvementis directed to making sure the heating elements are in constant contactwith the cassette to ensure the fluid in the fluid path is uniformlyheated to the desired temperature. Applicants are unaware of fluidwarming apparatuses for fluids designed to enter a patient that arematerially distinct from the apparatus disclosed in the '282 patent,except for the following invention.

SUMMARY OF THE INVENTION

The present invention is directed to a fluid warming container (a.k.a.,cassette) having an integrated heating element attached to thecontainer, not the warming device as conventionally done. The heatingelement provides thermal energy to the fluid contained in the container.The fluid contained in the container is designed to be injected and/ordelivered, eventually and normally immediately, into a patient.

These and other objects are solved by the present invention. Theinvention will be understood more fully, while still further objects andadvantages will become apparent, in connection with the followingdetailed description of a preferred embodiment thereof, illustrated inthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a fluid bag of the present invention;

FIG. 2 is cross-sectional view of a fluid bag in a warmer device of thepresent invention;

FIGS. 3 a-e are top plan views or cross-sectional views of variousembodiments of the fluid bag of the present invention;

FIG. 4 is an alternative embodiment of FIG. 2;

FIGS. 5 a and b; 6 a and b; and 7 a and b illustrate embodiments inwhich to apply a force to the fluid contained in the fluid bag;

FIG. 8 is an alternative embodiment of FIG. 1.

FIG. 9 is an alternative embodiment of FIG. 1.

FIG. 10 is an alternative embodiment of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a heating cassette 10 andalternatively, the heating cassette 10 with fluid compressioncapabilities. The cassette 10, as shown in FIG. 1, is at least one sheetof fluid impermeable material 12 having a fluid inlet 14, a fluid path16, and a fluid outlet 18. The cassette 10 is designed to be insertedinto a slot 20 of the warmer device 22, as illustrated in FIG. 2.

In one embodiment, the warmer device 22 is identical or similar to thewarmer device disclosed in the '282 patent, except for the heaterelements and the position of the temperature sensor. Accordingly, wehereby incorporate by reference the entire disclosure of the '282 patentin this application, minus the positions of the heater element and thetemperature sensor.

A main difference between the warmer device 22 of the present inventionand the warmer device of the '282 patent lies in the position of aheater element 30. In the '282 patent, the heater elements were theupper and/or lower boundary of the slot. The heater element waspositioned to contact the exterior surface of the cassette and transferthe heat generated by the heater element to the fluid in the fluid pathof the cassette.

The present invention has the heater element 30 as an integratedcomponent of the cassette 10. The heater element 30, in one embodiment,is any conductive material that generates resistance when an electricalcurrent passes through it, and therefore generates heat that istransferred to the fluid in the fluid path 16. Moreover, the conductivematerial 30 must be capable of being integrated into, within and/or ontothe cassette 10 by various methods, including and not limited toprinting, embossing, heat sealing, adhesion, polymerizing, orlithographing. These methods are known to those of ordinary skill in theart, and have been used extensively in the field of flexible conductivecircuits. Gaymar is unaware of using such technology for warming fluidsdesigned to enter a patient.

The fluid impermeable material 12 must allow thermal energy to transferinto the fluid path for the first embodiment wherein the conductiveelement is within and/or on the material 12. Alternatively, the material12 must allow an electrical current to pass through at least a portionof the fluid impermeable material 12 if the conductive element 30 is inthe interior of the material 12. An example of, and not limited to such,the fluid impermeable material is thin (like four thousandth of an inch(0.004″) thick) polyethylene. The fluid impermeable, thermal energytransfer material 12 may be a single sheet folded over 23 and sealed, byvarious known methods (heat welding, adhesive, sonic welding), atpredetermined portions 24 along the edges and within the interiorsection to form the fluid path 16 as shown in FIG. 1. Alternatively, thematerial 12 may comprise at least a first sheet 12 a and a second sheet12 b, as shown in FIG. 2, that are sealed, by various known methods, atpredetermined portions along the edges and within the interior sectionto form the fluid path 16. In any case, the material 12 is integratedwith a conductive material 30.

The heating element 30 can overlie the entire exterior surface 17 of thecassette 10 as shown in FIGS. 3 a and e, the entire exterior surface 17of one side of the cassette as shown in FIG. 3 b, the entire exteriorsurface 17 of the fluid path 16 on one or both sides of the cassette 10as illustrated in FIGS. 3 c and 3 a and b, predetermined portions ofexterior surface 17 of the fluid path 16 on one or both sides of thecassette as illustrated in FIGS. 1 and 3 a and b, or combinationsthereof.

The heating element 30 can be incorporated into the fluid impermeablematerial. Such conductive fluid impermeable materials are known to thoseof ordinary skill in the art. Examples of such conductive films can befound at, and not limited from such location, Bennett and Bennett inSpringfield, Ohio. For example, a conductive polyethylene bag can bemade from a single layer of carbon-loaded polyethylene. The conductivitydoes not depend on humidity. It is non-abrading, does not contaminatecomponents or fluids it comes in contact with and is groundable.

The heating element 30 can also be enclosed between the exterior surface17 of the fluid path 16 and a third sheet 12 c. The third sheet 12 c isdesigned to provide further protection to the heating element 30, asillustrated in FIG. 3 d. The third sheet 12 c can be sealed to thesingle sheet 12, the first sheet 12 a, the second sheet 12 b orcombinations thereof, at the edges, at predetermined portion of theedges, and/or at the interior surfaces, or combinations thereof. In thisalternative embodiment, the heater element 30 could be a heat transferfluid, like a Therminol fluid.

In yet another embodiment, the heating element can be on the interiorsurface 170 of the fluid path 16. In such embodiment the heating element30 is printed on the surface 170. Alternatively, the heating elementcould also be within and/or on the impermeable material to assist in thetransfer of the energy source, in most cases electricity and/or use ofinductive heat, to the heating element.

To allow the present invention to properly operate with a conductiveheating element 30, the warming device 22 has at least one electricalcontact 32, or direct wired, designed to transmit an electrical currentto the integrated heater element 30. The electrical contact 32 can be aspring or other device, actuating or not, that contacts the heaterelement 30 when the heating cassette 10 is positioned within the slot20. In one embodiment, the electrical contact 32 is not designed tomaterially block and/or materially restrict the flow of the fluid withinthe fluid path 16. The electrical contact 32 is merely designed tomerely contact the heater element 30, as shown in FIG. 1, to allowelectricity to travel from the warming device 22 to the heater element30 integrated with the heating cassette 10.

The electrical contact 32 can be positioned anywhere in relation to theheater element 30. There can even be multiple electrical contacts 32.The electrical contacts 32 can be positioned to contact (i) the topsurface 50 of the cassette 10 if the heater element 30 is below the topsurface 80 of slot 20 as shown in FIG. 1, (ii) the bottom surface 52 ofthe cassette 10 if the heater element 30 is over the bottom surface 82of the slot 20 as illustrated in FIG. 4, (iii) the side surface 54 ofthe cassette 10 as illustrated in FIGS. 3 and 4 if the heater element 30contacts or is adjacent to the corresponding side surface 84 of the slot20; or combinations thereof.

When operating, the warming device 10 interconnects to an electricalsource 40. The electrical source 40 delivers an electrical current tothe warming device 10, which in turn delivers the current to theelectrical contact and then to the heater element 30.

How is the temperature controlled in the warming device? The warmingdevice uses a plurality of devices to control the temperature. Forexample, it uses a sensor 90 as a resistance temperature detector (RTD).The sensor 90 can be positioned anywhere on or over the exterior 17 ofthe fluid path 16, the tubing into or out of the cassette, and/or theheater element 30. The sensor 90 can be thermally insulated from theheating element 30 by insulation using suitable materials or by physicallocation distal to the heater element, for example and not limited tothree layers 92 of Teflon.RTM. The sensor 90 is can be positioned on asecond spring or a second actuating/non-actuating device 31 (see FIG. 4)that can contact the desired portion of the cassette 10, and/or tubing.The sensor 90 is normally attached to the second device 31 by a layer ofhigh temperature adhesive 86. The normal, but not to be limited to suchdimensions, total distance from sensor 90 to the fluid in the cassetteis ten thousandths of an inch (0.010″). Suitable sensors are well knownand available in the art. (For example, a suitable sensor ismanufactured by Minco Products Inc., of Minneapolis, Minn.)

In FIG. 1, the applicants illustrate a conventional fluid path used influid cassettes. The design illustrated in FIG. 1 is known as acounter-flow fluid path. That fluid path has been determined to providea desired thermal exchange between the fluid and the heater elements;and the fluid exiting the cassette and the fluid entering the cassette10. By no means is the present fluid path design limited to thiscounter-flow design. In particular, the fluid path can be serpentine, oreven, though not normally desired, a straight path or random path, butthese paths can be used.

In any case, the counter-flow fluid path can be described as follows:The cold flow of fluid enters the cassette 10 at inlet port 14. Once thefluid is within the fluid path 16, a preferred fluid path entails havingthe fluid traverse down path 152. In relation to the fluid entering theinlet 14, the fluid turns left 90° to proceed down path 160. Path 160and the inlet 14/outlet 18 are on the opposite sides of the cassette 10.From path 160, the fluid turns another left 90° to enter path 154. Path154 directs the fluid to the front of the cassette (side of the inletand outlet 14, 18). Near the front of the cassette, the fluid againturns left. This time the turn is 180° into path 156. Path 156 directsthe fluid toward path 160. Prior to reaching path 160, the fluid turns180° to the right into path 158. From path 158, the fluid is directedtoward the outlet 18.

From outlet 18, the fluid can be directed toward a second warmer unit,or alternatively to a patient.

Fluid path 158 is normally the warmest fluid path portion and is locatedin the middle of the coldest path portion 152 and a colder path portion156, causing a thermal counter balance of energy. The sensor 90 isnormally located near outlet 18 where fluid exits the heat exchanger 16to ensure the fluid's temperature is at or near the desiredpredetermined temperature prior to entering the patient. The automatictemperature controller stabilizes at a preset temperature limit causinga thermal counter balance with the energy reservoir.

The described sensor in its specific location is one of many keys to thethermal control system. The sensor can be a simple on/off switch to analgorithmic controlled sensor. One example, which is in the middle ofthose two examples is a thermal feedback system used is a proportional,integral, derivative (PID) temperature controller. This is a controlmode with three functions. The “proportional action” dampens the systemresponse. “Integral” corrects for droop. “Derivative” seeks to preventovershoot and undershoot. The sensor input sampling rate is, for exampleand not limited to, 10 samples/second of the fluid's temperature exitingthe cassette 10. A thermal counterbalance of fluid exists from thecassette 10 compared to a predetermined set temperature which is thefeedback signal to a PID temperature controller, which is set forth inthe '282 patent. The temperature controller will adjust and replenishany energy lost to the cassette 10 through the heater element 30.

The primary PID temperature controller maintains an output temperatureof approximately 35° to 40° C. in the fluid over the flow range of 10 to300 ml/min for 10° C. fluid input. For 20° C. or above, the fluid inputmay be warmed to a flow rate of 500 ml/min. If the primary controllersenses a fluid temperature above 43° C. an audible alarm will also soundand cut off power to the energy reservoir. The unit will await a fluidtemperature drop below 43° C., or any other desired temperature desiredby the user, before turning off the audible alarm.

When the primary controller senses a fluid temperature below 34° C. anaudible alarm will also sound and automatically adjust power to theenergy reservoir, awaiting fluid temperature rise above 34° C. beforeturning off the audible alarm.

The temperature controller is recognized to be regularly available inthe art. The PID primary temperature controller 100 is, for example, aseries 935 auto tuning controller manufactured by Watlow Control ofWinona, Minn.

If the cassette temperature reaches a predetermined temperature, anaudible alarm will sound and power will cut off to the heating element30 and PID controller. The audible alarm can be programmed to beterminated, for example, by removing the power cord from the wallsocket. A safety cut-out switch is well known and available in the art.

As shown in the circuit diagram in FIG. 5 of the '282 patent, if thereis a catastrophic failure, and the temperature of the energy reservoirrises to 45° C., a safety cutout bimetallic switch which is embedded inthe warming device 22 cuts off all power to cassette 10. No audiblealarm is heard and the temperature display goes blank. Suitablebimetallic switches are well known and available in the art.

The device can also operate by battery power to make the device trulyportable.

Thus, to allow maximum user flexibility, especially important inemergency hospital care, a blood/fluid warming system is designed andprovided in which the cassette 10 is easily inserted into slot 20 ofwarmer device 22. For proper operation, the cassette 10 should beinserted into the slot 20 so the first device 32 contacts the heatingmaterial 30 and the second device 31 contacts the cassette 10.

To assist the cassette be properly inserted into the slot 20, thecassette can have aligning guide rails 48 a, b (as shown in FIG. 3 c )that correspond with mating slots 220 a, b, respectively, of device 22as illustrated in FIG. 4. The cassette 10 is continued to be insertedinto the slot 20 until the cassette can no longer be inserted therein.The stoppage of the cassette can be caused by a visual indicator 222that projects from the opening 224 on the opposite side of theinlet/outlet 14, 18 side of the slot 20. Alternatively, the cassette 10could have tubing 99 (as shown in FIG. 2) that forms a portion of theinlet 14 and outlet 18. The tubing 99 can stop the cassette 10 frombeing under-inserted and/or over-inserted into the slot 20.

As indicated above, the heating element 30 is any material that createsthe desired thermal energy to control the temperature of the fluid inthe cassette and/or tubing when an electrical current is passed throughthe heating element and is capable of being integrated with the cassette10 and tubing 99. The conductive material can also be anelectro-magnetic material. When an electrical current is passed throughthe material the electromagnetic material acts as a magnetic material.The electro-magnetic material receives the electrical current andgenerates the desired thermal energy and simultaneously is attracted toa corresponding magnetic or a second electromagnetic material(collectively referred to as the “other material”) on the opposite sideof the cassette 10. This embodiment is illustrated in comparisonanalysis of no current—FIGS. 5 a and 6 a—to current applied—FIGS. 5 band 6 b. By opposite side of the cassette, we mean the other material130 is either integrated with the cassette 10 opposite the conductivematerial 30 as illustrated in FIGS. 5 a and b, or is a side or a portionof the surface that defines the slot as illustrated in FIGS. 6 a and b.If the other material 130 is an electromagnetic material as illustratedin FIGS. 5 a and b, the other material 130 receives an electricalcurrent in the same way that the conductive material 30 receives itscurrent.

When the conductive material 30 is pressed toward the other material130, the conductive material 30 pushes the fluid toward the outlet bydecreasing the size of the fluid path (compare A to B in FIGS. 5 a andb, and 6 a and b).

Alternatively, the various devices 31, 32 can be interconnected to athird device 33. The third device 33 is an actuator that applies a force(as illustrated in comparison FIGS. 7 a and b—a downward force) to thedevices 31, 32. When that force is applied, the devices 31, 32 push intothe fluid path 16 (see analysis of A and B height differentials of thefluid path) to apply a forward force (seen by arrows) to exteriorsurface 17 of the cassette 10 to direct the fluid in the fluid path 16toward the outlet 16. Alternatively, the third device 33 can directlyapply the forward force to the exterior surface 17 of the cassette 10 todirect the fluid in the fluid path 16 toward the outlet 16. The timingof when the forward force is applied is controlled by the controllingdevice.

In a further alternative embodiment, the cassette has a fourth fluidimpermeable material 12 d, as illustrated in FIG. 8. This fourthmaterial 12 d is on the opposite side of the cassette 10 which has theheater element 30 thereon, or alternatively on the same side, whichmeans the fourth material 12 d can be the third material or bepositioned over the third material. The fourth material 12 d can besealed to the remaining cassette material (12; 12 a,b; 12 a,b,c) in thesame manner in which the third material is sealed to the othermaterials. Preferably, the fourth material 12 d is positioned to conformto the fluid path 16 and therefore has an inlet and an outlet thatcorresponds to the inlet 14 and outlet 18 of the fluid path. That way asecond fluid can be injected into a compression path positioned betweenthe fourth material 12 d and the remaining cassette material (12; 12a,b; 12 a,b,c).

The second fluid can be a gas or a liquid. Preferably, the second gas iseither water or air. In any case, the second fluid is occasionallypumped through the compression path to direct the fluid in the fluidpath toward the outlet. The second fluid can have any temperature.Preferably, the temperature of the second fluid corresponds with thetemperature of the heater elements. Controlling the temperature of thesecond fluid and directing the second fluid into the compression pathcan be accomplished with conventional devices known to those of ordinaryskill in the art.

The present warming device 22 can be positioned horizontally, verticallyor any direction there between. The warming device 22 can be positionedanywhere that is needed because it can have various adaptations toattach it to the desired device and/or in any location.

Turning to FIG. 9, the heating element 30, as indicated previouslyabove, can be wrapped in a cage-like manner (like chicken wire) or wireweave frame on the interior surface of the material (a.k.a., fluid path)for the tubing, within the tubing material, outside the delivery tube99, 199, or combinations thereof (the latter is the catheter tube). Thisdesign ensures that the heated fluid from the cassette 10 retains itsdesired temperature into the patient. The heating element 30 in thetubes can be interconnected to the same energy source as the heatingelements for the cassette, or alternatively to a second energy sourcewhich could be independent or dependent on the first energy source.

In addition to those alternative designs, the heating element can beshaped like streamers 400 as illustrated in FIG. 10 for the cassette 10and/or the tubes 99, 199. This streamer design can be on the exteriorsurface of the material, within the material itself, on the interiorsurface (a.k.a., fluid path) of the material, or combinations thereof.This streamer design can increase the surface area of the heatingelement, and possibly eliminate the need for a gap for the cassette inthe warming device. The electrical contact device 402 of the streamerscan be an electrical/magnetic device positioned on and/or over thestreamers. The electrical/magnetic device allows the cassette and/ortubes to contact the electrical source without the gap thereon. Thiselectrical/magnetic device can be incorporated in the other embodimentsof the present invention as well.

Having described the invention with regard to certain specificembodiments thereof, it is to be understood that this description is notmeant as a limitation since further modifications may now suggestthemselves to those skilled in the art, and it is intended to cover suchmodifications as fall within the scope of the appended claims.

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 44. A fluid warming system comprising a container thatcontains a fluid wherein the fluid is released from the containerthrough a tube, the tube directs the fluid to a patient; the tube has aheating element positioned on the interior surface of the tube so theheating element directly contacts the fluid, with the material the formsthe tubing, on the exterior surface of the tube; or combinationsthereof; the heating element is interconnected to a power source thatcontrols the temperature of the heating element which controls thetemperature of the fluid.
 45. The fluid warming system of claim 44wherein the container has a second heating element.
 46. The fluidwarming system of claim 44 wherein the heating element is streamer-like.47. The fluid warming bag of claim 1 wherein the heating element isstreamer-like.
 48. The fluid warming bag of claim 22 wherein the heatingelement is streamer-like.